下列生物学过程中体现了细胞全能性的是（　　）

    Each year thousands of____ (explore) and tourists visit the polar regions of the Arctic and Antarctica. But the increasing number of people travelling to the ends of the Earth' can have a negative effect____ fragile ecosystems. Should tourists____(allow) to visit polar regions?

    About 40,000 tourists visit Antarctica each year, More than five million travel to the Arctic and sub-Arctic. Transporting tourists to the regions ____(increase) ship and airplane traffic, adding to the risk of pollution, oil spills, and other ____(environment) damage. Because the places where wildlife is accessible ____(be) few in numbers, tourist traffic can become concentrated in specific areas,____ (put) Arctic vegetation at risk.

    Others say that access____ these very special parts of the world should not be restricted to only researches and scientist. Polar tourism allows people to develop deep personal connections with polar regions. “Those ____travel to the Arctic or Antarctica often become cheer leaders for supporting those places” Jim Sano, vice president for travel and____(conserve) at World Wildlife Fund, told TFK.